Digital Logic

What is the voltage range considered to be valid logic low input in a TTL device operating at 5 volts?

Answer

Zero to 0.8 volts.

In 5-V TTL, any input from 0 to 0.8 V is guaranteed to be read as a valid logic low.

Source: FCC Element 3 question pool, 3E

Not the answer

  • 5.2 to 34.8 volts.
  • -2.0 to -5.5 volts.
  • 2.0 to 5.5 volts.

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